Apparatus for forming metal strips of curved cross-sections



O 1954 H. w. NIEMAN ET AL 2,692,003 APPARATUS FOR FORMING METAL STRIPSOF CURVED CROSS-SECTIONS Filed Nov. 7. 1951 2 Sheets-Sheet l %w 4 mm.

INVENTORS ATTORNE I 1954 H. w. NIEMAN ETAL APPARATUS FOR FORMING METALSTRIPS OF CURVED CROSS-SECTIONS Filed Nov. 7, 1951 2 Sheets-Sheet 2INVENTORS 51031 zVuznzan Henge 0. BY

@TORNE Patented Oct. 19, 19 54 UNITED STATES PATENT OFFICE APPARATUS FORFORMING METAL STRIPS IOF CURVED CROSS-SECTIONS Application November 7,1951, Serial No. 255,172

4 Claims. (Cl. 153-32) Our invention relates to apparatus and method forconverting fiat or substantially flat material into a trough like shapeand more particularly to apparatus and method for forming a relativelythin strip or sections of trough like shape which is straight lengthwisethereof and which is especially useful for making slats for Venetianblinds.

The material usually employed in the making of Venetian blind slats is ahard rolled relatively thin steel strip or a strip of other metal with ahard temper, the physical characteristics of the material being suchthat straightening after the forming operation is either impracticableor if practicable requires additional undesirable operations. Heretoforein the common forming practice it has been found impossible to produceunder normal conditions straight products of this character in oneoperation and therefore it has been the usual practice to employ eitherbefore or after the forming operation other operations comprisingvarious mechanical steps to physically work the material. By the use ofour invention all such steps can be dispensed with and straight productsof the desired transverse shape can be obtained in a single operation.

One object of our invention is to provide a forming die assembly of suchconfiguration that it will form in one operation a straight strip orsection longitudinally and of trough shaped cross section from arelatively thin flat or substantially fiat metal strip or section.

Another object of our invention is to provide a forming device throughwhich a flat or substantially fiat rolled metal strip is passed and inone operation is formed into a straight strip longitudinally of curvedcross section and which requires no further shaping or straighteningwhen used as slat material for Venetian blinds.

A specific object of our invention is to provide the forming dies of aconfiguration which will support the strip while it is being acted uponto transversely bend the same so that its edges and center whiletraveling in different paths during such bending operation will travelin paths of approximately the same length and produce a strip of acurved cross section which is straight longitudinally thereof.

The novel features of our invention will be more fully understood fromthe following description and drawings in which Fig. 1 is a sideelevation of an apparatus embodying the forming device of our invention;

Fig. 2 is a section taken on line 22 of Fig. 1 and showing the guidingrolls of our device;

Fig. 3 is a section taken on lines 33 of Fig. 1;

Fig. 4 is a section taken on lines ii 5 of Fig. 1 and showing thepulling rolls of the device;

Fig. 5 is a view of the grooved forming dies of our invention;

Fig. 6 shows diagrammatically a bending operation where the center ofthe strip passes in a straight path and the edges thereof pass in alonger path;

Fig. '4 shows diagrammatically a bending operation where the edges ofthe strip pass in a straight path and the center passes in a longerpath;

Fig. 8 shows diagrammatically the bending operation of our inventionwhere the edges and the center of the strip while passing in differentpaths pass in paths of approximately the same length;

Figs. 9 and 9a show the strip made by the bending operation of Fig. 6;

Figs. 10 and 10a show a strip made by the bending operation of Fig. '7;

Figs. 11 and 11a show a strip made by the bending operation of Fig. 8.

Referring to the drawings, i l designates an apparatus with which theforming device it em bodying our invention is shown assembled. Ourimproved forming device it, as shown in the drawings, comprises guidingrolls ii and it through which the fiat or substantially flat strippasses, the roll it being provided with guiding flanges 19, which serveto center the entering strip in the forming device, a pair of groovedforming dies 20 and 2|, a convex roller die 2?. cooperating with thedies 2d and El to transversely bend the flat strip into a strip 55' ofcurved cross section and driven pinch rolls 23 and 2d, havingcooperating contour surfaces matching the shape of the formed strip 25,which are shown provided with a pulley 53 which is driven by any wellknown driving means, such as an electric motor operatively connected tothe pulley 553 by means of a belt and pulley to draw the strip materialthrough the apparatus. Other means, which may be supplementary to oralternative to the pinch rolls may be used to apply force to the end ofthe strip to pull it through the forming device. A bracket 25, uponwhich the forming die at and the rolls 23 and E i are mounted, is shownpivotally mounted at 26 on the apparatus approximately concentric withthe axis of the roller 22 and is capable of vertical adjustment by meansof the adjusting device 2"! which has its end 23 mounted on the bracket25 and its upper threaded end 3! cooperating with a threaded member 29attached 3 to the frame 36. The upper end of the adjusting device 2'? isprovided with means 32 to rotate the adjusting device 2? to raise orlower the bracket 25. The roller die 22 is adjustably mounted on theframe 30 by means of the member 33 upon which the bearing 49 of theroller die 22 is eccentrically mounted so that the roller may beadjusted with relation to the forming dies 20 and 2!. The member 33 isprovided with a nut '33 to retain the roller die 22 and its bearing dupon the member 33. A lever 4'? which is mounted on the bearing 49 isprovided for adjusting the roller die 22 upon the loosening of the nut38.

The forming dies 20 and 2!, shown in Figs. 1 and 5, which constitute adie assembly, have a passageway 45 in the upper surface thereofextending from end to end of the dies and are clearly shown in Fig. 5.The die 23 is broadly flared at its entrance end 34 where the flat orsubstantially flat strip enters the passageway 18 of the die 26, thewalls 41 forming the sides of the passageway rapidly converge from theentrance end 3 to the opposite end 35 of the die 29 and the inner bottomportion 42 of the die is gradually relieved an increasing amount alongits center portion from the flared end 3 to the opposite end 35, thusproducing at its end 35 a die portion of U-shaped formation. The end 36of the die 2! which is adjacent the end 35 of the die 29 has a U-shapeddie portion of approximately the same shape and dimensions as the dieportion at the end 35 of the die 29. The roller die 22 extends withinthe iJ-shaped die portions of the dies 2c and 2!. Adjacent the ends 35and 36 of the dies 2% and 2i, respectively, the radius of the dies aswell as the radius of the forming face 5-3 of the roller die 22 isconsiderably smaller than the required radius of th finished formedproduct so that the strip when it is being formed beneath the roller 22is depressed a greater amount than required for the finished shape ofthe strip 55 so as to allow for the natural spring back of the materialafter it passes from beneath the roller 22. The side walls M of the die2! diverge from its end 36 to its exit end 3? and the bottom wall 55tapers gradually upwardly from its end 35 to its exit end 3? and formsan arcuate portion adjacent said end 3'! which conforms approximately tothe shape of the finished strip l5.

In forming a substantially straight longitudinal strip or section curvedin cross section from a flat or substantially fiat rolled relativelythin strip in accordance with our invention, the forming dies 28 and Elare as shown in Fig. 1, so that the strip in passing through the dies2%) and 2| with its center portion depressed out of its normal pathbeneath the roller 22 during the transverse bending of the strip has itsedges 39 supported by the side walls M and id of the dies 29 and 2i,respectively, so that said edges travel in a predetermined path and theedges 39 and the center M! of the strip while shown following differentpaths during the bending of the strip are shown traveling in paths ofapproximately the same length, as diagrammatically shown in Fig. 8, andproduces a strip which is straight longitudinally as shown in Figs. 11and 11a.

In dies with their bottom surfaces in a straight line the length of thepaths traveled by the edges of the strip are longer than the pathtraveled by the center portion of the strip during the bending operationas diagrammatically shown in Fig. 8, and a with a longitudinal bend asshown Fig. 9 will be produced and in dies where the 4 edges of the striptravel in a substantially straight path and the center travel in alonger path during the bending operation as diagrammatically shown inFig. '7, the opposite efiect on the strip to that shown in Fig. 6 willtake place and the formed strip will have a longitudinal, bend as shownin Fig. 10.

It is essential in a product such as a trough shaped section for aVenetian blind slat that all longitudinal elements of the section be ofthe same length so that the slat will be straight longitudinally.Therefore, since a curved section is formed from a flat or substantiallyflat strip the strip must undergo some local changes during thetransverse bending operation and since the final formed curved productmust be straight lengthwise any changes lengthwise in one portion of asection of the strip must be balanced by an equivalent change lengthwisethroughout the other portions of the section. The assembly of ourinvention as shown in Fig. 1, which includes our novel grooved dieassembly 20 and 24 as clearly shown in Fig. 5, is particularly adaptabler'or forming strips or sections curved in cross section which are usefulfor making Venetian blind slats, as the forming dies of the as semblageare so constructed and positioned that in the transverse bending of thestrip any changes lengthwise in the center and the edges of the stripmust be equivalent due to the edges and the center of the strip passingthrough paths of approximately equal length, as diagrammatically shownin Fig. 8, thereby producing a strip curved in cross section andstraight lengthwise in one operation from a flat or substantially flatstrip or section of metal.

Even though the paths of the edges and center of the strip are of equallength from the entrance to the exit end of the dies, during the bendinglocal differentials of length are bound to occur between these pointsand the strip must undergo some local shortening or lengthening in theforming operation. Since the final formed product must be straight theshortening or lengthening must be balanced by an equivalent amount ofshortening or lengthening throughout the section. Considering the pieceof relatively thin strip in the process of forming between the rollerdie and the grooved dies, the center material is disposed naturally toaccept compressive stress without buckling and the edges must also becarefully supported as shown in Fig. 8 to accept compressive stresswithout buckling, otherwise differential changes in length between thecenter and edge portions may occur to cause the edge portions to berelatively longer than the center portion in the fil'lished material, asshown in Fig. 6, without the possibility of any correction of thiscondition by adjustment of the dies since such correction wouldnecessitate the application of tension to the center portions andcorresponding compression to the edges. The success of our formoperationis therefore dependent on the particular type of die members and theirproper relation as shown in Fig. l of the drawings so that edge andcenter changes of length of the material being acted, upon shall beequivalent, as disclosed in Fig. 8.

In operation a strip of flat or of substantially fiat formation isthreaded through the guiding rolls H and E8, the forming dies 20 and 21beneath the roller die 22 and through the pinch rolls 23 and 24 whichare driven through the pulley 50 by suitable means to pull the stripthrough the forming dies to form the strip into a strip straightlengthwise and of curved cross section. During the passage of the stripthrough the forming dies its center portion is depressed beneath theroller die 22 to transversely bend the strip and the edge portions ofthe strip are supported by the side walls 4| and 44 so that the edgesand the center of the strip will pass through the dies during thebending thereof in different paths, but in paths of approximately equallengths, as shown diagrammatically in Fig. 8, and the strip produced insaid dies will be straight longitudinally thereof. The strip formed inthis single operation of the desired transverse form and straightlengthwise is especially adaptable for use as slat material for Venetianblinds without any further forming or straightening operations.

From the foregoing, it is evident that we have devised an efficientforming device which, in one operation, transforms a flat orsubstantially flat relatively thin strip material into a strip straightlengthwise thereof and of curved cross section, which is especiallyadaptable for Venetian blind slats.

While we have shown our invention in one form, it will be obvious tothose skilled in the art that it is not so limited but is susceptible tovarious changes and modifications without departing from the spiritthereof.

We claim:

1. An apparatus for forming in one operation a substantially flat rolledmetal strip into a substantally straight longitudinal trough shapedsection, comprising a forming die assembly having a substantiallyU-shaped die portion and a broadly flared guiding portion adjacent theentrance end of said die assembly merging into said U-shaped portion andan arcuate flared portion adjacent the exit end of the forming die andmerging into the U-shape portion and a die having a convex portionextending into the U-shaped die portions to force the center portion ofthe strip being formed from its normal path into a path beneath theconvex portion of the die to transversely bend said strip, said dieassembly comprising supporting means for the edges of the strip toretain said edges in a path approximately the same length as the paththrough which the center portion of the strip travels during thetransverse bending of the strip.

2. A forming die assembly comprising a' pair of members disposed in endto end relation and having passageways in their faces extending from endto end of the members, one of said die members having a broadly flaredentrance, side walls along its passageway converging from said flaredentrance to the opposite end of said member, the bottom of the die beingof arcuate formation and tapering downwardly from the flared entrance tothe end of the die member and together with the side walls forming a dieportion adjacent said end of approximately U- shape formation, the otherof said die members having a die portion adjacent the first mentioneddie portion of the same dimensions and shape as the first mentionedU-shaped die portion, and an arcuate exit portion, side walls divergingfrom the inner end and merging into the arcuate end portion of said diemember, the bottom of the die member being of arcuate formation andtapering upwardly from the inner end thereof and merging into thearcuate exit end of said die member, and a bending memher having aconvex portion extending into said U-shaped portions of theaforementioned pair of members.

3. The combination in an apparatus for forming, in one operation, astraight metal strip of curved cross section of an elongated stationaryforming die through which an elongated substantially flat relativelythin metal strip is passed, said forming die comprising a broadly flaredentrance portion, a flared exit portion, and a U-shaped portionintermediate said flared portions into which said entrance portion andsaid exit portion merge and a die having a convex portion cooperatingwith the U-shape portion to transversely bend said strip and to forcesaid center portion of the strip out of its normal plane beheath theconvex portion of said die, and supporting means integral with saidforming die for supporting the edges of the strip to retain the edges ofthe strip in a path of a length approximately equal to the length of thepath of travel of the center portion of the strip during the transversebending of the strip, whereby the edge portions of the strip can acceptcompressive stress without buckling during the deflection of the centerportion of the strip by the convex portion of said die.

4. An apparatus for forming in one operation from a substantially flatrolled relatively thin metal strip a section or strip having a straightlongitudinal shape and a curved cross section comprising a die having aconcave forming portion adjacent the center thereof and flaredsupporting portions adjacent each end thereof and merging into saidconcave portion and a die having a convex portion extending into saidconcave portion to force said strip out of its normal path and to bendsaid strip transversely, and means constituting supports for the edgesof the strip adjacent the flared portions and the concave portions toretain said edges in a predetermined path while the center portion isbeing deflected from its normal path during the transverse bending ofthe strip and thereby forming a strip straight longitudinally and ofcurved cross section.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 901,637 Mckenzie Oct. 20, 1908 1,069,869 Eynon Aug. 12, 19131,681,790 Slate Aug. 21, 1928 1,708,872 Coates Apr. 9, 1929 2,145,867Fentress Oct. 17, 1936 2,072,831 Solenberger Mar. 2, 1937 2,073,174Potter Mar. 9, 1937 2,337,047 Hunter Dec. 21, 1943 2,338,678 Wilson Jan.4, 1944 2,346,990 Oftedal Apr. 18, 1944 2,370,215 Wilson Feb. 27, 19452,600,442 Stanius June 17, 1952

